[ntp:questions] Reasons of NTP not to use GPS source

Igor Pavlov pavlov.ig at gmail.com
Tue Sep 17 08:05:42 UTC 2013


Thanks, Brian.

I'll do all these things.
Now will try to fix problem with PPS: it's level 3.3V, and serial port
seems to not recognising such low level.
Now playing with time2 parameter and my GPS now stoped getting "x".

I can't understant one thing.
Should system time be fluently corrected by NTP so in some term offset of
active ("*") source would be close to 0?



2013/9/17 Brian Inglis <Brian.Inglis at systematicsw.ab.ca>

> On 2013-09-16 01:00, Igor Pavlov wrote:
>
>> Hi!
>>
>> I am using GPS-receiver based on Geos-1m chip (
>> http://www.geostar-navigation.**com/en/navigation_05.html<http://www.geostar-navigation.com/en/navigation_05.html>
>> )
>>
>> I connected it to serial port and configured NTP.
>> It becomes unused by NTP: when do ntpq -p reuest ti puts "x" near
>> "GPS_NMEA(1)" record.
>>
>> What reasons can be for this?
>>
>> Example of "ntpq -p" output
>>
>>       remote           refid      st t when poll reach   delay   offset
>>   jitter
>> ==============================**==============================**
>> ==================
>> xGPS_NMEA(1)     .GPS.            0 l   14   16  377    0.000  -303.07
>> 4.292
>> *stratum1.net    .PPS.            1 u   62   64  377   62.800  -68.052
>>   43.693
>> +dl120g7.naviteh 194.190.168.1    2 u   58   64  377   30.151  -100.04
>>   52.432
>> +89.221.207.113  192.36.133.25    2 u    -   64  377   10.006  -105.88
>>   64.279
>>
>
> See David Taylor's pages at
> http://www.satsignal.eu/ntp/**NTP-on-Windows-serial-port.**html<http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html>
> and linked pages at top for a lot of details about setup, but keep
> everything really simple to start, then change one thing at a time after
> running for a while and checking the results.
>
> Check your GPS comms and config using the supplied setup software:
> are you seeing NMEA output at your selected 115.2kbps?
> which sentences $GPRMC, etc.?
> has your receiver completed its initial survey and is it reporting Active,
>  and reasonable mode, position, altitude, UTC date and time in sentence
> $GPRMC?
> how many satellites is your receiver tracking to what precision in
> sentences $GPGGA, $GPGSA, $GPGSV?
> is your receiver set to 1Hz PPS rather than 5Hz updates?
> is PPS toggling DCD high for about 100ms at the start of ecah second?
> Note that Windows recognizes only low to high DCD transitions as PPS.
>
> If your mouse cursor starts jumping around, unplug your RS232 cable,
> *disable* the Windows mouse driver which just got loaded on your serial
> port, plug in your RS232 cable, and restart if required.
>
> If all that looks good, next try disabling everything but PPS and $GPRMC
> sentence output from your receiver config, and use only your server
> 127.127.20.n line, without any fudge settings, plus your backup Internet
> servers, in ntp.conf.
> Then restart NTP and see if ntp.log shows something like:
> ...
> 14 Aug 12:50:38 ntpd[####]: GPS_NMEA(#) serial /dev/gps# open at 4800 bps
> 14 Aug 12:50:38 ntpd[####]: GPS_NMEA(#) 8011 81 mobilize assoc #####
> ...
> 14 Aug 12:50:39 ntpd[####]: GPS_NMEA(#) 802b 8b clock_event clk_no_reply
> 14 Aug 12:50:39 ntpd[####]: Using user-mode PPS timestamp for GPS_NMEA(#)
> ...
> 14 Aug 12:50:57 ntpd[####]: GPS_NMEA(#) 8034 84 reachable
> 14 Aug 12:50:57 ntpd[####]: GPS_NMEA(#) 904a 8a sys_peer
> ...
> Now ntpq -p should show * beside your GPS_NMEA(#) entry:
>
>      remote           refid      st t when poll reach   delay   offset
>  jitter
> ==============================**==============================**
> ==================
> *GPS_NMEA(#)     .GPS.            0 l   12   16  377    0.000   -0.011
> 0.021
> and if you defined statsdir ... and statistics clockstats in ntp.conf you
> should see entries in clockstats.yyyymmdd like:
> 56512 7.123 127.127.20.# ...
> ...$GPRMC,000006,A,5108.####,**N,11411.####,W,000.0,000.0,**
> 080813,014.7,E,D*0F
>
> If nothing seems to be working, try restarting the NTP service - at times
> it seems to have issues getting going properly in various ways.
>
>
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>



-- 
Игорь Павлов


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